*EDIT*This cap is now replaced with GM part # 23159210The price has increased to around $50 online.

So There are several threads about this gas cap and having it coded by a dealer for $50, or having a locksmith do it.
If you dont have extra cash or your key code you can follow my instructions and get it done in less than 10 minutes.

For those of you that do not know, this cap works with your existing side cut key. About $22 from dealer, $15 or less online
GM part # 22790846
AC Delco # GT344

The tumblers are listed as 1L, 1R, 2L, 2R, etc. these are left or right specific.
One side of the lock cyinder has 2 keyhole slots and one has 3. The side with the 3 keyhole slots is the LEFT side.
There are 2 tumblers per side, the 3rd one on the left side is for the brass retainer clip.

Grab one tumbler that has a L in it and insert it into the first keyhole slot.

Hold the tumbler centered in cylinder and insert your key all the way.

Slide the sleeve (tab end first) over the cylinder.
If it stops at the tumbler it is the wrong one. (pic below)

If correct it should slide all the way up and rotate 90 degrees.

Once first position is correct leave it in and repeat for other left tumbler.

Then find both right side tumblers the same way.
Now carefully remove each tumbler and remember its location.
(the 5,6,7,8 below is the order of the cut positions if you get the code from the dealer)

Insert 2 springs (I did right side 1st)

Insert tumblers.

Repeat for left side.

Insert your key, and slide over the cylinder sleeve.
Make sure it rotates smoothly.

If everything is good insert the last spring and the brass keeper till it clicks in place.

Check for full operation one last time.Once you install the cylinder into the cap it will not come out.

Align the 3 tabs in the cap, and the 3 grooves of the cylinder.

Press together, till it clicks. You may have to rotate the handle, while holding the white part of the cap. Make sure you get those 2 tips on the end of the cylinder to line up.

When I saw all the parts that come in the bags I was worried, but getting them togther was really easy. Good job with the pictures. I have had mine for over a year and this keeps me from leaving the keys in the car when I fuel up.

I just did this not 10 minutes ago. Easy peasy. And it DOES fit 2010s for anyone wondering like I was. (book doesn't show it fitting 2010 for some reason)

Just a couple of notes. The pin holding it onto the cap can be a mofo. It's plastic and will pop off, but you may mangle it if you're not careful. I almost did.

Also, obviously since it has more moving parts, it's heavier than the original cap by far, so be careful not to let it drop when you're removing the key so it doesn't clunk the quarter panel. More potential for damage.

[QUOTE=el ess X;5818213]
Just a couple of notes. The pin holding it onto the cap can be a mofo. It's plastic and will pop off, but you may mangle it if you're not careful. I almost did. QUOTE]
Yeah I didn't talk about removing the strap to the door. Your on your own there

So There are several threads about this gas cap and having it coded by a dealer for $50, or having a locksmith do it.
If you dont have extra cash or your key code you can follow my instructions and get it done in less than 10 minutes.

For those of you that do not know, this cap works with your existing side cut key. About $22 from dealer, $15 or less online
GM part # 22790846
AC Delco # GT344

The tumblers are listed as 1L, 1R, 2L, 2R, etc. these are left or right specific.
One side of the lock cyinder has 2 keyhole slots and one has 3. The side with the 3 keyhole slots is the LEFT side.
There are 2 tumblers per side, the 3rd one on the left side is for the brass retainer clip.

Grab one tumbler that has a L in it and insert it into the first keyhole slot.

Hold the tumbler centered in cylinder and insert your key all the way.

Slide the sleeve (tab end first) over the cylinder.
If it stops at the tumbler it is the wrong one. (pic below)

If correct it should slide all the way up and rotate 90 degrees.

Once first position is correct leave it in and repeat for other left tumbler.

Then find both right side tumblers the same way.
Now carefully remove each tumbler and remember its location.
(the 5,6,7,8 below is the order of the cut positions if you get the code from the dealer)

Insert 2 springs (I did right side 1st)

Insert tumblers.

Repeat for left side.

Insert your key, and slide over the cylinder sleeve.
Make sure it rotates smoothly.

If everything is good insert the last spring and the brass keeper till it clicks in place.

Check for full operation one last time.Once you install the cylinder into the cap it will not come out.

Align the 3 tabs in the cap, and the 3 grooves of the cylinder.

Press together, till it clicks. You may have to rotate the handle, while holding the white part of the cap. Make sure you get those 2 tips on the end of the cylinder to line up.

I just did this not 10 minutes ago. Easy peasy. And it DOES fit 2010s for anyone wondering like I was. (book doesn't show it fitting 2010 for some reason)

Just a couple of notes. The pin holding it onto the cap can be a mofo. It's plastic and will pop off, but you may mangle it if you're not careful. I almost did.

Also, obviously since it has more moving parts, it's heavier than the original cap by far, so be careful not to let it drop when you're removing the key so it doesn't clunk the quarter panel. More potential for damage.

2) The new gas cap strap has this push-in connector already installed on it, ready to pop in place, and your old one has the same. To remove the old one--push-in connector + strap and all--get some needle nose pliers and carefully squeeze the barbs on the back side of the push-in connector and it will come out easily. You can see the springy plastic barbs on your new one so you know what to look for. Then just push your new one back in its place. You see that it is easier to do without the fuel door in the way. Now just slide your door back on and you are good to go!

So, I just set up this locking gas cap, and installed the cylinder into the plastic gas cap. I thought I did it correctly because the key moved smoothly and I am absolutely positive all the tumblers are perfect, but I'm second guessing if this is functioning correctly now. Maybe this is a crazy question, but when I insert the car key into the gas cap, when I turn it to the right, the lock refuses to let my car keys out of lock. It literally is stuck in there, but when I turn the key 90 degrees to the left to its starting position, the car key comes right out. Now, this can't possibly be normal for the gas cap to "lock" my keys into position when turned fully one of the directions, or is it?

I just installed mine on the car and it works perfect! I did do it correctly following these directions. I had no idea that the key stayed in the gas cap while unscrewing/unlocking it. Once it's fully loosened to take it off, then you can take the key out.

Thanks again original poster! Your directions made it sooooo much easier put it together.